1. Field of the Invention
The present invention relates to an electronic component with bump electrodes, and to a manufacturing method thereof. More particularly, the present invention relates to a semiconductor chip, printed wiring board, or other electronic component with bump electrodes such as a ball grid array (BGA), and to a manufacturing method thereof.
2. Description of the Related Art
The need for higher density in the packaging of electronic components on printed wiring boards, ceramic boards, and the like has increased in recent years, and bare chip packaging has attracted attention as a technology that satisfies this need. In bare chip packaging, the trend is in the direction of adopting face-down mounting or flip-chip bonding, which is accomplished by interposing bumps between a semiconductor chip and the electrode pads of a wiring board, instead of using the conventional face-up mounting, which is accomplished by wire bonding of electrical connections between the semiconductor chip and the board wiring. In face-down mounting, bump electrodes are formed in advance on the mounting surface of an unpackaged semiconductor chip or wiring board to allow bumps to be interposed between the semiconductor chip and the electrode pads of the wiring board.
FIGS. 12a–12e depict an example of a conventional method for manufacturing a semiconductor chip with bump electrodes. In this conventional method, a specific metal mask 44 is prepared for the semiconductor chip 40, as shown in FIG. 12a. A wiring pattern that contains electrode pads 42 (only the electrode pads 42 are shown) is formed on the surface of the substrate 41 in the semiconductor chip 40. An insulating film 43 for protecting the wiring pattern is further laminated and formed over the wiring pattern on the substrate 41. The insulating film 43 has openings 43a at positions that correspond to each of the electrode pads 42. The metal mask 44 has openings 44a formed in advance at positions that correspond to the electrode pads 42 and openings 43a. 
The openings 44a and electrode pads 42 are then aligned, and the metal mask 44 is placed on the semiconductor chip 40, as shown in FIG. 12b. Solder paste 45 containing a specific solder powder is subsequently fed by printing to the openings 44a in the metal mask 44 and the openings 43a in the insulating film 43, as shown in FIG. 12c. The metal mask 44 is then removed from the semiconductor chip 40, with the solder paste 45 left behind, as shown in FIG. 12d. A heating treatment is subsequently conducted in order to temporarily melt the solder powder in the solder paste 45, and bump elements 46 are formed on the electrode pads 42, as shown in FIG. 12e. 
The semiconductor chip 40 provided with bump electrodes in this manner is flip-chip bonded to a wiring board 50, as shown in FIG. 13a. Specifically, the electrode pads 42 of the semiconductor chip 40 and the electrode pads 52 of the wiring board 50 are electrically and mechanically connected via the bump elements 46. With such flip-chip bonding, an adhesive or an underfiller 60 is commonly packed between the semiconductor chip 40 and wiring board 50, as shown in FIG. 13b. The underfiller 60 protects the bump elements 46 for connecting the electrode pads, and also protects the mounting surfaces of the semiconductor chip 40 and wiring board 50. With such an underfiller 60, connection reliability can be maintained for a long time in this type of flip-chip bonding.
However, so-called open (non-contact) defects often occur in the bump electrode structure of the conventional method for manufacturing an electronic component with bump electrodes described above with reference to FIGS. 12a–12e. An open defect is a defect in which the bump-forming material primarily balls up on the insulating film 43 during the heating treatment described above with reference to FIG. 12e, and gaps are formed between the electrode pads 42 and bump elements 46, as shown, for example, in FIGS. 14a and 14b. An electrical connection between the electrode pads 42 and bump elements 46 cannot be adequately formed if an open defect occurs. The open defect shown in FIG. 14a assumes a condition in which the entire bump-forming material is balled up on the insulating film 43, and is apt to occur when solder paste is used as the bump-forming material in the above-described manner. The open defect shown in FIG. 14b assumes a condition in which some of the bump-forming material remains on the electrode pads 42 and the rest of the material is balled up on the insulating film 43, and is apt to occur when molten solder or solder plating is used as the bump-forming material.
The electrode pads 42 formed on the substrate 41 of the semiconductor chip 40 serve as part of the wiring formed in a pattern on the surface of the substrate 41, and have the same specific thickness as the other wiring locations. The insulating film 43 for covering and protecting this wiring is required to have a minimum given thickness in accordance with the thickness of the wiring. The greater the thickness of the insulating film 43 is made in order to make wiring protection more secure, the deeper the electrode pads 42 are located in the openings 43a of the insulating film 43. The deeper the electrode pads 42 are located in the openings 43a, the more likely it is that open defects such as those shown in FIG. 14 will occur. By contrast, the thinner the insulating film 43 is made in order to suppress such open defects, the more likely it is that insulation defects will be caused by the formation of pinholes in the insulating film 43. Specifically, the ability of the insulating film 43 to cover the wiring will be adversely affected. In addition, sometimes it becomes impossible to handle a fine pitch if the diameter of the openings 43a in the insulating film 43 is increased.
Meanwhile, it is desirable that the bump elements 46 be made higher within the constraints of the electrode pitch. This is because the gap between the semiconductor chip 40 and the wiring board 50 must be widened in order to allow this gap to be more adequately filled with the underfiller 60 for maintaining the reliability of connections, as shown in FIG. 13b. The surface curvature of higher bump elements 46, that is, larger-volume bump elements 46, tends to be lower, so the degree to which such higher bump elements 46 can penetrate into the openings 43a tends to decrease as well. The less the degree is to which the bump elements 46 can penetrate into the openings 43a, the more likely it is that open defects such as those shown in FIGS. 14a and 14b will occur.
It is thus necessary to increase the thickness of the insulating film beyond a certain value and to increase the height of the bump elements beyond a certain value at a certain electrode pitch of an electronic component with such bump electrodes. This is why open defects such as those shown in FIGS. 14a and 14b often occur in the currently employed electronic components designed as conventional bump electrode structures with progressively narrower electrode pitches.